One of four words
Why energy.
Nothing comes from nothing. Whatever is here, the atoms and the stars and the thoughts in your head, all of it had to come from somewhere, there is no other option, and so something must have been there first, something capable of becoming everything else that followed.
Modern physics has, more or less by accident, arrived at the same conclusion. Matter turns out to be condensed energy, fields are energy, forces are exchanges of energy, and the solid world, when you look closely enough at it, dissolves into vibration and pattern. What we used to call substance turned out to be something more fundamental, behaving.
Energy is the most defensible candidate we have for the thing that has always been here.
I do not mean energy the way a physicist measures it, in joules and watts, I mean the broader and older sense the word always had, the capacity to be and to move and to do and to become, the source that everything else is made out of.
This word on its own, though, gives you a cold universe. Energy with no consciousness and no intelligence and no love in it is just a mechanism, an engine running for no one and meaning nothing, and that is exactly why the description needs four words and not one. Energy is what the rest gets built on, but you do not stop at the thing you build on.